System and method for turbocharging an engine

ABSTRACT

A turbocharger system, in certain embodiments, includes a compressor, a turbine, a shaft coupling the compressor to the turbine, and a turbo casing configured to improve pressure recovery, wherein the turbo casing includes a non symmetrical geometry configured to improve flow towards an exhaust outlet.

BACKGROUND

The disclosure relates generally to a system and method of improving theperformance of a turbocharger for a compression-ignition engine and,more specifically, to a system and method for adjusting the position ofand parameters of turbocharger components.

Turbochargers include a turbine and a compressor that may be connectedby a shaft. The turbine is located in a turbine stage section of theturbocharger, and the components in the turbine stage are importantfactors in turbocharger efficiency and performance. In particular,components that affect exhaust flow, such as a turbo casing anddiffuser, may allow undesirable loss of energy from exhaust flow if notproperly designed.

BRIEF DESCRIPTION

A turbocharger system, in certain embodiments, includes a compressor, aturbine, a shaft coupling the compressor to the turbine, and a turbocasing configured to improve pressure recovery, wherein the turbo casingincludes a non symmetrical geometry configured to improve flow towardsan exhaust outlet. Another embodiment includes a method that includesflowing exhaust through an exhaust diffuser having a bell mouthconfigured to improve pressure recovery within a turbo machine, andflowing the exhaust through an annular torus shaped chamber of a turbocasing having a cross sectional area that expands in a circumferentialdirection toward an exhaust port.

DRAWINGS

These and other features, aspects, and advantages of the presentdisclosure will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a block diagram of an embodiment of a system having an enginecoupled to a turbocharger with an improved turbine stage;

FIG. 2 is a cutaway side view of an embodiment of a turbocharger havingan improved turbine stage;

FIG. 3 is a detailed cutaway side view of an embodiment an improvedturbine stage, as illustrated in FIG. 2;

FIG. 4 is a cutaway end view of an embodiment of a turbocharger havingan improved turbine stage;

FIG. 5A is a detailed cutaway side view of an embodiment of a turbocasing of an improved turbocharger taken along line 5A-5A of FIG. 4;

FIG. 5B is a detailed cutaway side view of an embodiment of a turbocasing of an improved turbocharger taken along line 5B-5B of FIG. 4;

FIG. 5C is a detailed cutaway side view of an embodiment of a turbocasing of an improved turbocharger taken along line 5C-5C of FIG. 4;

FIG. 6A is a detailed cutaway side view of an embodiment of a turbocasing of an improved turbocharger, illustrating cross sectional areasof an exhaust diffuser and a turbo casing;

FIG. 6B is a cutaway end view of an embodiment of a turbocharger havingan improved turbine stage;

FIG. 7 is a chart of the circumferential location within twoturbochargers plotted against a ratio of cross sectional areas of theturbo casing to the exhaust diffuser, as shown in FIGS. 6A and 6B; and

FIG. 8 is a chart of expansion ratio plotted against normalized turbineefficiency for two turbocharger designs.

DETAILED DESCRIPTION

One or more specific embodiments of the present disclosure will bedescribed below. In an effort to provide a concise description of theseembodiments, all features of an actual implementation may not bedescribed in the specification. It should be appreciated that in thedevelopment of any such actual implementation, as in any engineering ordesign project, numerous implementation-specific decisions must be madeto achieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

When introducing elements of various embodiments of the presentdisclosure, the articles “a,” “an,” “the,” and “said” are intended tomean that there are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements. Anyexamples of operating parameters and/or environmental conditions are notexclusive of other parameters/conditions of the disclosed embodiments.

As discussed in detail below, various configurations of turbine stagecomponents may be employed to reduce energy loss from restricted exhaustflow and to improve turbocharger performance. In particular, an exhaustdiffuser with a bell mouth portion may be added to the turbine stagealong with a repositioning of a rotor, thereby avoiding an increase inbackpressure that may occur when modifying the diffuser. For example, abell mouth may be added instead of a straight edge to extend a diffuser,along with a repositioning of the rotor disc closer to the inlet andtransition section of the turbocharger, thereby improving pressurerecovery as the exhaust flows out of the turbine stage. In addition, theturbo casing may be modified to work in conjunction with the exhaustdiffuser to improve pressure recovery, thereby increasing turbochargerefficiency. The embodiments discussed below improve turbochargerperformance and efficiency by modifying and repositioning components inthe turbine stage and exhaust path. The embodiments and pressurerecovery improvements may apply to turbochargers, turbo machines, turboexpanders, turbines, and other turbine machinery.

FIG. 1 is a block diagram of a system 10 having a turbocharger 12coupled to an engine 14, in accordance with certain embodiments of thepresent technique. The system 10 may include a vehicle, such as alocomotive, an automobile, a bus, or a boat. Alternatively, the system10 may include a stationary system, such as a power generation systemhaving the engine 14 coupled to a generator. The illustrated engine 14is a compression-ignition engine, such as a diesel engine. However,other embodiments of the engine 14 include a spark-ignition engine, suchas a gasoline-powered internal combustion engine.

As illustrated, the system 10 includes an exhaust gas recirculation(EGR) system 16, an intercooler 18, a fuel injection system 20, anintake manifold 22, and an exhaust manifold 24. The illustratedturbocharger 12 includes a compressor 26 coupled to a turbine 28 via adrive shaft 30. The EGR system 16 may include an EGR valve 32 disposeddownstream from the exhaust manifold 24 and upstream from the compressor26. In addition, the system 10 includes a controller 34, e.g., anelectronic control unit (ECU), coupled to various sensors and devicesthroughout the system 10. For example, the illustrated controller 34 iscoupled to the EGR valve 32 and the fuel injection system 20. However,the controller 34 may be coupled to sensors and control features of eachillustrated component of the system 10, among many others.

As illustrated in FIG. 1, the system 10 intakes air into the compressor26 as illustrated by arrow 36. In addition, as discussed further below,the compressor 26 may intake a portion of the exhaust from the exhaustmanifold 24 via control of the EGR valve 32 as indicated by arrow 38. Inturn, the compressor 26 compresses the intake air and a portion of theengine exhaust and outputs the compressed gas to the intercooler 18 viaa conduit 40. The intercooler 18 functions as a heat exchanger to removeheat from the compressed gas as a result of the compression process. Asappreciated, the compression process typically heats up the intake air,and thus is cooled prior to intake into the intake manifold 22. Asfurther illustrated, the compressed and cooled air passes from theintercooler 18 to the intake manifold 22 via conduit 42.

The intake manifold 22 then routes the compressed gas into the engine14. The engine 14 then compresses this gas within various pistoncylinder assemblies, e.g., 4, 6, 8, 10, 12, or 16 piston cylinderassemblies. Fuel from the fuel injection system 20 is injected directlyinto engine cylinders. The controller 34 may control the fuel injectiontiming of the fuel injection system 20, such that the fuel is injectedat the appropriate time into the engine 14. The heat of the compressedair ignites the fuel as each piston compresses a volume of air withinits corresponding cylinder.

In turn, the engine 14 exhausts the products of combustion from thevarious piston cylinder assemblies through the exhaust manifold 24. Theexhaust from the engine 14 then passes through a conduit 44 from theexhaust manifold 24 to the turbine 28. In addition, a portion of theexhaust may be routed from the conduit 44 to the EGR valve 32 asillustrated by arrow 46. At this point, a portion of the exhaust passesto the air intake of the compressor 26 as illustrated by the arrow 38,as mentioned above. The controller 34 controls the EGR valve 32, suchthat a suitable portion of the exhaust is passed to the compressor 26depending on various operating parameters and/or environmentalconditions of the system 10. As depicted, the exhaust gas drives theturbine 28, such that the turbine rotates the shaft 30 and drives thecompressor 26. The exhaust gas then passes out of the system 10 andparticularly the turbine 28, as indicated by arrow 48. As compressor 26is driven, additional air intake occurs, thereby improving performance,power density, and efficiency in the engine by providing additional airfor the combustion process.

As will be discussed in detail below, optimization and modification ofcertain components in the turbine stage portion of the turbocharger mayreduce energy loss and improve performance of the turbocharger system.For example, the disclosed embodiments may include a modifiedconfiguration of the turbo casing to reduce exhaust flow separationthereby improving exhaust flow to a muffler and improving turbochargerefficiency. In addition, the arrangement and design of the exhaustdiffuser and axial location of the turbine stage improve pressurerecovery within the system, further enhancing exhaust flow and systemefficiency through reduced back pressure on the engine. The disclosedembodiments also improve turbocharger performance across variousconditions, including during both high and low speed operation. Theseenhancements improve performance and fuel efficiency of the turbochargersystem and engine.

FIG. 2 is a sectional side view of an embodiment of improvedturbocharger 12. In the embodiment, turbine stage portion 50 includesseveral components and modifications that improve efficiency andperformance of the turbocharger 12. As depicted, compressor end 52includes compressor 26 (e.g., compressor blades), which is attached toshaft 30 and turbine 28 (e.g., turbine blades). In the arrangement, therotation of turbine 28 causes compressor 26 to rotate, therebycompressing air within the turbocharger 12 to increase air density forintake manifold 22. In the embodiment, turbo casing 56 encompasses acavity which may be described as torus shaped, and allows exhaust toflow and exit, as depicted by arrow 48. Turbocharger exhaust may flowinside turbo casing 56 and be directed from lower section 58 toward theexhaust port in upper section 60. Exhaust may be routed into turbocasing 56 by exhaust diffuser 62, which features a bell mouth or curveshaped cross-section 64, thereby enhancing exhaust flow and improvingpressure recovery in turbocharger 12. For example, exhaust flow fromdiffuser 62 may encounter less resistance as it flows toward exhaustoutlet and upper portion 60, thereby improving performance andefficiency. Turbine buckets 66 may be radially located on turbine 28,thereby rotating the turbine 28 as exhaust flows through the turbinebuckets 66. Exhaust may flow through nozzle ring 70 en route to turbinebucket 66 and turbo casing 56. Exhaust may enter a portion ofturbocharger 12 via transition section 72, which may be optimized toenhance exhaust flow of the improved turbocharger design 12. Forexample, turbocharger exhaust may flow through optimized transitionsection 72, nozzle ring 70, turbine buckets 66, exhaust diffuser 62, andturbo casing 56, thereby driving rotation of turbine rotor 28 andflowing exhaust through the improved exhaust diffuser 62 and turbocasing 56. The diagram also includes sectional lines 4 that illustrate asectional plane used in FIG. 4. In an exemplary embodiment, transitionsection 72 may have a curvature configured to reduce flow separation ofthe flow entering turbocharger 12. For example, transition section 72may have two inlets having walls 71 that gradually curve inward, ratherthan abruptly angled, to reduce the likelihood of flow separation.

FIG. 3 is a detailed sectional side view of an embodiment ofturbocharger 12, as shown in FIG. 2. As depicted, turbine stage portion50 has several improvements that are designed to improve turbochargerperformance and enhance exhaust flow through exhaust diffuser 62 andturbo casing 56. In the embodiment, the cavity enclosed by turbo casing56 may include an axial or lateral distance 73 between casing walls 74and 75, which may vary depending upon the circumferential locationwithin the torus-shaped turbo casing 56. Specifically, due to turbocasing cross section geometry 76, distance 73 may be less in lowerportion 58 than distance 78 in upper portion 60. As illustrated,interior casing wall 74 expands in a direction of exhaust flow fromlower casing portion 58 to upper casing portion 60. Further, an angle ofan interior wall 74 of the lower half of the turbo casing, includinglower portion 58, is about 75 to 80 degrees relative to an axis throughthe shaft 30. In addition, upper casing cross section geometry 80illustrates a change in casing geometry as compared to lower casinggeometry 76. In an embodiment, the edge of bell mouth 64 may be adistance 81 from the turbine 28. For example, distance 81 may be about 3to about 7 inches. Turbocharger exhaust may flow through turbine buckets66 and exhaust diffuser 62, as indicated by arrow 82 into turbo casing56. In lower portion 58, exhaust flow may be routed upward toward anexhaust port 83, as indicated by arrow 84. Exhaust may flow fromdirection 84 to direction 86 toward the exhaust port 83, whereindistance 78 and other turbo casing components enable improved exhaustflow and reduced flow attachment, thereby improving turbochargerefficiency.

In an exemplary embodiment, bell mouth 64 of exhaust diffuser 62 may beshaped and positioned to improve pressure recovery in turbocharger 12.For example, bell mouth 64 may have an axial distance 85 and a radialdistance 87 from a wall of turbo casing, which distances may beconfigured to improve pressure recovery. In an embodiment, the bellmouth 64 extends axially (in the direction of shaft 30 axis) about30-50% into a cavity of the turbo casing 56. Specifically, the distance78 minus distance 85 may be about 30-50% of distance 78, therefore thebell mouth 64 extends about 30-50% into the cavity. Further, in a firstbottom portion 58 of the bell mouth 64 extends about 50% into thecavity. In a second portion, near exhaust outlet 83 and opposite portion58, the bell mouth 64 extends about 30% into the cavity.

The diagram also includes dashed lines depicting an alternate exhaustdiffuser profile 88, which may be described as a flat diffuser profile,as compared to the curved cross section 64 of bell shaped diffuser 62,which increases turbocharger efficiency. The improvements illustrated inturbine stage portion 50, including an expanding cross sectional area ofturbo casing 56 toward an exhaust flow port as well as bell shapedexhaust diffuser 62, may lead to improved turbocharger efficiency andperformance, thereby reducing fuel consumption and emissions. Inaddition, turbine rotor 28 may be shifted axially outward in direction89, thereby increasing the length of shaft 30 by about 15-20% to furtherenhance the effects of exhaust diffuser 62 and turbo casing 56improvements. In addition, a ratio of the distance 81 to a turbinebucket height or distance 87 is about 1.4 to about 3.4.

FIG. 4 is a sectional end view of an embodiment of an improvedturbocharger 12, as shown in FIG. 2. In the embodiment, turbo casing 56is configured to direct exhaust flow toward an exhaust port 83. In theembodiment, the turbo casing 56 has an interior geometry that variesfrom lower section 58 to upper portion 60, e.g., area scheduling of thecross section of the cavity within turbo casing 56. Distance 90 is aradially measured distance within turbo casing 56 near lower section 58of the torus shaped turbo casing 56. Distance 90 is less than a distance92, which is measured within the turbo casing cavity in a radialdirection approximately 90 degrees relative to distance 90 within thetorus-shaped turbo casing 56. In addition, the cross sectional area atthe location where distance 90 is measured may be at least approximately30-50% less than the cross sectional area at the location distance 92 ismeasured. Accordingly, the volume within the turbo casing cavity expandstoward an exhaust port 83 located near upper portion 60, improving andenhancing performance and efficiency of turbocharger 12. As depicted, achange in the geometry of turbo casing wall 94 illustrates the change incross section area of the turbo casing 56. In addition, exhaust may flowfrom exhaust diffuser 62 downward into turbo casing 56, as shown byarrow 96. Turbo casing 56 may then route the exhaust flow incircumferential direction 98 toward upper portion 60, wherein the volumewithin the turbo casing 56 expands in the direction of exhaust flow.Finally, exhaust may flow through upper portion 60, as indicated byarrow 100, wherein the volume within turbo casing 56 is much larger thanthe volume of turbo casing 56 near lower portion 58. Cross section lines5A-5A, 5B-5B, and 5C-5C, illustrate the planes used to create sectionalviews of turbo casing 56 to depict circumferential views of geometrieswithin turbocharger 12. Specifically, line 5A-5A may be described as ata 180 degree angle to reference line 101, line 5B-5B may be described asat a 135 degree angle, and line 5C-5C may be described as at 90 degreeangle.

FIG. 5A is a detailed cutaway side view of an embodiment of turbo casing56 of an improved turbocharger 12, taken along line 5A-5A of FIG. 4. Inthe embodiment, turbo casing 56 has a smaller cross sectional area inlower section 58, as compared to an upper section 60 of the turbocharger12. Accordingly, distance 73 between casing walls may be less than inportions of the turbo casing 56 located near the exhaust port 83. Inaddition, turbo casing geometry 76 is also different than upper portionsof turbo casing 56 as the turbo casing changes toward an exhaust outlet.Further, as previously described, exhaust may flow from an exhaustdiffuser 62 outward and downward within the turbo casing 56 and may beredirected by the geometry 76 toward an exhaust port 83.

FIG. 5B is a detailed cutaway side view of an embodiment of turbo casing56 of an improved turbocharger 12, taken along line 5B-5B of FIG. 4. Asdepicted, the sectional view is taken at a plane that is about 45degrees relative to the sectional plane view of FIG. 5A. In theembodiment, turbo casing 56 has a larger cross sectional area than thecross section in lower section 58. The distance 102 between casing wallsmay be larger than a similar distance 73 in lower section 58. The areascheduling of the cavity within turbo casing 56 is achieved in part bythe wall geometry 103, which improves exhaust flow.

FIG. 5C is a detailed cutaway side view of an embodiment of turbo casing56 of an improved turbocharger 12, taken along line 5C-5C of FIG. 4. Asdepicted, the sectional view is taken at a plane that is about 90degrees, or perpendicular in orientation to, the sectional plane view ofFIG. 5A. In the embodiment, turbo casing geometry 104 may be configuredto enhance an improved exhaust flow through the turbo casing 56 byexpanding the turbo casing cavity of the exhaust flows toward theexhaust port 83. As such, distance 105, between turbo walls 74 and 75may be larger distance than distances 102 and 73 (from FIGS. 5B and 5A).The embodiment of turbo casing 56 and improved turbine stage portion 50includes improved geometry and component orientations to enable enhancedturbocharger 12 performance, improved efficiency, improved exhaust flow,and reduced back pressure in the turbocharger system 12.

FIG. 6A is a detailed sectional side view of an embodiment of turbocasing 56 of an improved turbocharger 12. FIG. 6B is a sectional endview of an embodiment of an improved turbocharger 12. Areas shown inFIGS. 6A and 6B illustrate areas that are included in a ratio of anexhaust hood or turbine casing area to a diffuser inlet annulus area. Inthe embodiment shown in FIG. 6A, the sectional view is taken 180 degreesfrom reference line 101. At this point, turbo casing 56 may encompass across-sectional cavity area 108 that may be referred to as the turbocasing area. Line 110, along with turbo casing 56, encompass turbocasing area 108. In FIG. 6B, a diffuser inlet annulus area 112 isillustrated, wherein the area 112 is the area of the bottom half of theinlet opening area from the buckets 66 to the diffuser 62. As depicted,the area 112 is the inlet annulus area below a line 113 that is in thecenter of the inlet annulus. Areas 108 and 112 may be used to illustratethe area scheduling to improve exhaust flow within turbine stage portion50. The geometry and cross sectional area (108) of turbo casing 56changes through the circumference of the torus-shaped cavity. Further,in an exemplary embodiment, the diffuser 62 geometry and area (112)created by the illustrated sectional view is uniform throughout thecircumference of the torus-shaped cavity. Accordingly, a ratio of theturbo casing area 108 to diffuser inlet annulus area 112, takenthroughout the circumference of the turbocharger 12, may be useful inillustrating the improved efficiency and flow characteristics of theturbo casing 12 design. The gradual increase of the turbo casing area108 in the direction of exhaust flow, towards outlet 83, may bedescribed as a non symmetrical geometry of turbo casing 56, leading tothe improvements discussed below. The ratio of areas throughout thecircumference of turbocharger 12 are illustrated in chart form in FIG.7.

Specifically, FIG. 7 is a chart illustrating the above-described arearatios (e.g., area 108 to area 112) as they relate to a circumferentialposition where the section plane is located within improved turbocharger12. As depicted, the chart 114 plots a circumferential position whereinthe cross sectional area 108 of the turbo casing 56 is taken at varioussectional planes through turbocharger 12 as illustrated in FIG. 4.Further, the ratio of the exhaust diffuser area to diffuser inletannulus area is illustrated along axis 118. The ratio plotted in chart114 is turbo casing area 108 at each cross section along thecircumference of the turbocharger 12 divided by the constant diffuserinlet annulus area 112. Line 120 is a plot of area ratio data from anembodiment of a turbocharger stage portion that does not feature theimproved turbo casing design and therefore has a less gradual change incross sectional area (108 in FIG. 6A), which can cause significant flowlosses. Line 122 illustrates the area ratio (e.g., 108 to 112) and itsgradual change of cross sectional area for the exhaust turbine casing asplotted against the position within the turbocharger 12 relative toreference line 101. In addition, area 112 is a constant value for bothlines 120 and 122.

As depicted, the circumferential position 116 (e.g., horizontal axis)are data points taken between the 60 degree plane and the 300 degreeplane relative to a plane through reference line 101 (FIG. 4). In thechart 114, the 60 degree data points are a ratio of area measurementstaken through a plane 60 degrees in a clockwise direction relative to aplane through line 101. The 90 degree data points are a ratio of areameasurements taken through a plane about 90 degrees clockwise to theplane through line 101. In addition, the data points at 300 degrees arearea measurements taken at 300 degrees in a clockwise direction relativeto the plane through line 101. As shown, the gradual change in arearatio (e.g., 108 to 112) within the turbo casing 56, shown by line 122,allows for a gradual volume expansion and therefore a smoother flow ofexhaust through the turbo casing, thereby improving flow andturbocharger performance. Conversely, line 120 shows an alternativeturbo design with abrupt changes in area ratios, as shown near 90 and270 degree data points, resulting in less efficient and less smoothexhaust flow. For the gradual change illustrated by line 122, the arearatio 118 may be characterized as an area ratio change of about 8% toabout 30% per 30 degrees, between the circumferential positions of 180to 300 degrees in a clockwise direction. Further, plot 122 of the arearatios 118, taken at circumferential locations 116 in counterclockwisedirections between 60 and 300 degrees, relative to vertical planethrough line 101 of the turbo casing 56 may vary between about 0.42 andabout 1.15.

In the depicted arrangement, turbo casing 56 is disposed downstream fromthe exhaust diffuser 62, wherein the turbo-casing comprises atorus-shaped chamber leading to an exhaust outlet 83. In addition, thetorus-shaped chamber has a cross-sectional area that progressivelyincreases by at least about 40 percent from about the 180 degreesposition to about the 270 degree position in an annular direction towardthe exhaust outlet 53. Further, the progressive increase incross-sectional area is represented by the area ratio plot 122 nonsymmetrical torus-shaped chamber between about 60 and about 300 degreesrelative to a vertical plane centered through line 101, wherein the arearatio plot 122 varies between about 0.42 and about 1.15.

FIG. 8 is a chart of normalized turbine efficiency plotted againstexpansion ratio for a turbocharger system. The expansion ratio may bedescribed as a turbine inlet pressure divided by a turbine exit pressurein absolute terms. The expansion ratio measurements may be taken attransition section 72 (turbine inlet pressure) and exhaust outlet 83(turbine outlet pressure). Expansion ratio is an input to FIG. 8 whichcan be used to identify the operation of a turbine, the benefit is shownon the vertical axis using the normalized turbine efficiency. In chart124, a normalized turbine efficiency 128 is plotted against expansionratio 126, thereby showing turbocharger 12 performance improvements asdiscussed above. Normalized turbine efficiency 128 is a way to comparethe level of actual turbine performance to peak turbine performance atvarious expansion ratios by dividing the actual turbine efficiency ofthe turbo design by the peak turbine efficiency of the improved turbo.Accordingly, data plot 130 illustrates a design of a turbocharger 12with an exhaust diffuser and turbo casing which does not include theimproved components that have been optimized for exhaust flow. Incontrast, data plot 132 illustrates the improved turbocharger efficiencyachieved by the previously illustrated optimized turbo casing design andexhaust diffuser along with other turbine stage 50 components.

As depicted, the peak turbine efficiency of the improved turbo 132occurs at an expansion ratio of about 2.7, which is a normalized turbineefficiency of 1. A comparison of data plots 130 and 132 illustrate thatthe improved turbocharger 12 components, as discussed above, may resultin optimal and improved turbocharger efficiency. Specifically, thegradual geometry changes in turbo casing 56 and improvements in the bellshaped exhaust diffuser 62 provide improved exhaust flow and efficiencythrough area scheduling within the turbocharger 12. As shown in thechart 124, at low expansion ratios (1.5 for example), the improvedturbine 132 resulted in about 3% improvement and at higher expansionratios (3 for example), the improved turbine 132 resulted in about 8%improvement.

While only certain features of the disclosure have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the disclosure.

1. A turbocharger, comprising: a compressor comprising compressorblades; a turbine comprising turbine blades; a shaft coupling thecompressor to the turbine; and an exhaust diffuser disposed downstreamfrom the turbine blades, wherein the exhaust diffuser comprises a bellmouth configured to reduce backpressure and improve an exhaust flowdownstream; a turbo-casing disposed downstream from the exhaustdiffuser, wherein the turbo-casing comprises a torus-shaped chamberleading to an exhaust outlet disposed on and centered on a second sideopposite from a first side, the torus-shaped chamber has across-sectional area that progressively increases by at least about 40percent from a center of the first side in about the first 90 degrees inan annular direction toward the exhaust outlet in the second side. 2.The turbocharger of claim 1, wherein the progressive increase incross-sectional area is represented by an area ratio of thecross-sectional area of the torus-shaped chamber divided by a diffuserarea of the bell mouth, and the area ratio is taken through planes atcircumferential locations in a counterclockwise annular directionbetween about 60 and about 300 degrees relative to a vertical planecentered through the exhaust outlet in the second side, wherein the arearatio varies between about 0.42 and about 1.15.
 3. The turbocharger ofclaim 1, wherein a ratio of a length of the bell mouth in an axialdirection to a turbine bucket height in direction generally crosswise tothe bell mouth length is about 1.4 to about 3.4.
 4. The turbocharger ofclaim 1, comprising the turbo casing configured to improve pressurerecovery, wherein the turbo casing expands in volume in acircumferential direction of flow through an annular chamber to anexhaust outlet.
 5. The turbocharger of claim 1, wherein an angle of aninterior wall of the second side of the turbo casing is oriented atabout 75 to 80 degrees relative to an axis through the shaft.
 6. Theturbocharger of claim 1, wherein the bell mouth extends about 30-50% ofthe distance of the width of the turbo casing in a direction parallel toan axis of the shaft.
 7. The turbocharger of claim 1, comprising anengine coupled to the turbocharger system.
 8. The turbocharger of claim1, wherein the turbine is configured to create a cavity within the turbocasing with a non symmetrical geometry.
 9. The turbocharger system ofclaim 1, wherein the turbo casing comprises a torus shaped cavity.
 10. Aturbocharger, comprising: a compressor; a turbine; a shaft coupling thecompressor to the turbine; and a turbo casing configured to improvepressure recovery, wherein the turbo casing includes a non symmetricalgeometry configured to improve flow towards an exhaust outlet.
 11. Theturbocharger of claim 10, wherein the turbo casing comprises a torusshaped cavity, wherein a cross sectional area of the torus shaped cavityincreases in a direction of exhaust flow towards an exhaust outlet,thereby reducing a flow separation.
 12. The turbocharger of claim 11,wherein an angle of an interior wall of the turbo casing is oriented atabout 75 to 80 degrees relative to an axis through the shaft.
 13. Theturbocharger system of claim 10, comprising an exhaust diffusercomprising a bell mouth, wherein the bell mouth and the turbine areconfigured to improve pressure recovery and enhance exhaust flow througha turbo casing.
 14. The turbocharger of claim 13, wherein a ratio of alength of the bell mouth in an axial shaft direction to a turbine bucketheight in direction generally crosswise to the bell mouth length isabout 1.4 to about 3.4.
 15. The turbocharger of claim 13, wherein thebell mouth extends about 30-50% of the distance of the width of theturbo casing in a direction parallel to an axis of the shaft.
 16. Amethod, comprising: flowing exhaust through an exhaust diffuser having abell mouth configured to improve pressure recovery within a turbomachine; and flowing the exhaust through an annular torus shaped chamberof a turbo casing having a cross sectional area that expands in acircumferential direction toward an exhaust outlet.
 17. The method ofclaim 16, comprising wherein flowing the exhaust through an annulartorus shaped chamber comprises flowing the exhaust through a nonsymmetrical geometry of the turbo casing.
 18. The method of claim 16,wherein flowing the exhaust through an annular torus shaped chambercomprises flowing the exhaust through the chamber wherein a first arearatio at a portion of the chamber opposite the exhaust port is about30-50% less than a second area ratio of the chamber at a circumferentiallocation about 90 degrees relative to the first cross sectional area.19. The method of claim 16, wherein flowing the exhaust through anannular torus shaped chamber comprises flowing the exhaust through thechamber wherein an angle of an interior wall of the torus shaped chamberis oriented at about 75 to 80 degrees relative to an axis through aturbine shaft.
 20. The method of claim 16, wherein the bell mouthextends about 30-50% of the distance of the width of the turbo casing ina direction parallel to an axis of a turbine shaft